Piezoelectric crystal cabinet



Oct. 29, 1946. s. A. BoKovoY 2,410;041

PIEZOELECTRIC CRYSTAL CABINET Filed April 1, 1943 4 Sheets-Sheet 1 INVEN TOR.

Oct. 29, 1946. s. A. BOKOVOY 2,410,041

PIEZOELECTRIC CRYSTAL CABINET Filed April 1, 1943 4 Sheets-Sheet 2 0 w 14 m M w INVENTOR. SAMUEL ABo/rovoY 12W J) ATTORNEY Oct. 29, 1946. 5BOKQVOY 2,410,041

PIEZOELECTRIQ CRYSTAL CABINET Filed April 1, 1943 4 Sheets-Sheet 3 13INVENTOR.

Patented Oct. 29, 1946 PIEZOELECTRIC CRYSTAL CABINET Samuel A. Bokovoy,Verona, N. J assignor to Federal Telephone and Radio Corporation, NewYork, N. Y., a corporation of Delaware Application April 1, 1943, SerialNo. 481,427

7 Claims.

This invention relates to enclosed cabinet mountings especially adaptedfor piezo-electric crystals and provided With an improved arrangementfor maintaining the crystals at uniform temperature during wide changesin circumambient temperatures.

The mounting includes a cabinet construction comprising a plurality ofnested chambers with the crystals in the central chamber, provided witha thermostat-controlled heating element. A feature of the invention is aprovision of a novel construction and arrangement of the chambers,thermostat and heater which will eiiectively re tard the transfer ofoutside temperature changes to the crystal chamber and facilitate theoperation of the heater to compensate for such changes before they canreach the crystal chamber. The invention includes the use of an improvedin-, ternal chamber wall construction made of metal having good thermalconductivity arranged to provide uniformity of heat transfer to thethermostat and from the heater.

A further purpose is to provide a temperaturecontrolled cabinet suitablefor mounting a plurality of piezo-electric crystals arranged so thatthe, various crystals can be connected into circuits in any desiredmanner without disturbing the cabinet. Another object is the provisionof an improved crystal cabinet of the indicated type which is adaptedfor mounting in a standard type of pin socket.

Other objects and advantages will appear from the following descriptionconsidered in connection with the accompanying drawings, in which: v.Fig. 1 is a front elevation of a cabinet embody- I ing the inventionwith parts broken away, the

connecting leads being omitted;

Fig. 2 is a transverse section on line 22 of Fig. 1;

Fig. 3 is a vertical section on line 33 of Fig. 2;

Fig. 4 is a vertical section on line 4-4 of Fig. 2; and

Fig. 5 is a diagram of circuit connections.

The cabinet I0 comprises an outer base ll of insulating materialprovided with a plurality of hollow contact pins P set into the lowerface of the base, together with a positioning stud l2 provided with alongitudinal lug l3, said contact pins, stud and lug being of the typeusually employed on radio tube bases, arranged for insertion in tubesockets of the type ordinarily employed in radio apparatus.

An outer housing or hollow cover 14 of insulating material is fitted tobase I l to form a completely enclosed chamber. In the form illustratedthe housing I4 is generally rectangular in crosssection, being providedwith enlarged vertical corner portions l5 (Fig. 2); and the base It isprovided with housing positioning lugs l8 fitting against the side wallsof housing l4 intermediate the enlargements IS. A suitable gasket IIwhich may be of natural or synthetic rubber or the like is interposedbetween base I l and housing [4, the latter being held in place byscrews 18 extending upwardly through the corners of base ll into theenlarged corner portions l5 (Fi 4).

The piezo-electric crystals are mounted on inner base 20 whichis formedof insulating material and mounted on a pedestal 2| by screw 22 (Fig. 3)which is preferably countersunk and covered with insulating material 23such as glyptal resin. A rectangular positioning bar 24 may be fittedinto registering slots in the contiguous faces of the inner base 20 andpedestal 2|.

Suitable crystal supports are mounted on inner base 20 and areadvantageously arranged to provide proper support for a plurality ofpiezo-electric crystals, together with the appropriate electrodes andleads which advantageously extend through the base 20 and are connectedto the contact pins P. In the form illustrated three sets of crystalmounting spring clips 25 are supported on base 29, each including acontact spring 26 engaging one face of a crystal 21, and a nonconductingpost 28 engaging the opposite face and extending into a socket 29 (Fig.4) in base 2! The clips 25 are arranged to support three crystals 2! inparallel position equally spaced from each other and from parallelmargins of base 20. The clips for each crystal are arranged with thecontact springs 26 engaging opposite faces of the crystal, which isprovided with metallic surface contact elements such as metal platinextending over the opposite sides of the crystal in known manner. A lead36 extends from each contact spring 26 through a registering hole 3| inbase 20 into the channel 32 extending around and beneath the lowermargin of the base 20 and communicating with the upper ends of hollowpins P into Which the leads 30 pass, each lead being connected to theassociated pin by a solder tip 33 in the usual manner.

A wall made of a metal having good thermal conductivity is mounted oninner base 20 surrounding the crystals, and forms with outer housing I4an outer compartment 35. The wall carries a suitable thermostat and aheater located in the outer compartment. In the form illustrated thewall is in the form of a metal housing 36 advantageously made ofaluminum and fitting over the outer face of base 20, being suitably heldin place thereon as by screws 31. The heater consists of a winding 38 ofsuitable heater wire such as nichrome wound on the outer face of housing36, and may be held in place by insulating varnish. The thermostat 39 isof the standard enclosed bimetallic type with terminals at opposite endsand is mounted on the upper part of housing 36, extruding throughopenings at opposite sides of the housing with its terminals 49projecting into the outer compartment 35.

An inner crystal housing 41 of insulating material is advantageouslymounted on inner base 20 surrounding the crystals 21 and located withinthe metal housing 36. In the form illustrated the inner housing 4| has alower edge fitting snugly against the base 20 and is held removably inplace thereon by downwardly projecting tongues 42 (Fig. 4) at oppositesides fitting snug- 1y against the inner walls of registering recessesin the outer portions of base 20. The walls of the inner housing 4| areadvantageously spaced from the metal housing 36 and form an inner orcentral crystal compartment 42 and an intermediate or centralcompartment 43 between housings 4 and 38.

One end of the heater winding 38 is connected to one terminal 40 of thethermostat 39 while the other end of said winding as well as theopposite terminal 40 of the thermostat are connected by suitable leadsextending downwardly through the outer chamber 35 and channel 32 toappropriate contact pins P to which they are electrically connected inthe manner already indicated. The terminal 40 of thermostat 39 to whichthe winding 38 is connected may also be connected through a suitablelead to another pin P in similar manner to facilitate the connection ofa condenser across the thermostat. A suitable arrangement for connectingthe crystals 21, heater winding 38 and thermostat 39 to the variouscontact pins is shown diagrammatically in Fig. 5.

In the arrangement described and illustrated the crystals 2'! arelocated in an insulating dead air chamber 42 surrounded by a dead airchamber 43. Any change in the ambient temperature outside of the outerhousing [4 will be conducted gradually to the outer compartment 35 whereit will affect thermostat 39 promptly through conduction from both endsof the thermostat and through the metal housing 36. This will result inprompt energizing of the heater winding 38 when the temperature dropsbelow the normal temperature for which the thermostat is set andpromptly corrects the temperature drop in the outer compartment 35before it has an opporunity for appreciable transmission through theintermediate compartment 43 and inner housing II to the crystalcompartment 42. The transmission of temperature changes to the lattercompartment through the bases is negligible owing to the very thick baseconstruction, the reductions in the conducting path by the use of arestricted pedestal 2| and the absence of good thermally conductingparts.

The arrangement has been found so effective in practice that it hasproven to be capable of limiting the variations in the rate of crystaloscillation caused by changes in temperature to not more than aboutcycles per million during ambient temperature changes between 48 and +60Fahrenheit and even with substantial variations in heater voltages, suchas changes between 22 and 28 volts. The cabinet i extremely compact andsmall, and is arranged for ready construction and assembly as well asconvenient installation and replacement.

The parts referred to as made of insulating material are formed frommaterials having not only the necessary electrical insulating propertiesbut also high thermal insulating value. Various synthetic resins havethe requisite qualities and are adapted for ready molding or pressinginto parts of the types illustrated and described.

What is claimed is:

1. A temperature-controlled piezo-electric crystal mounting comprisin abase, an outer housing mounted on the base, said base and housing beingformed of thermal insulating material, a thermally conducting metalhousing spaced from the outer housing, a heater and a heater-controllinthermostat mounted on the metal housing, and an inner housing enclosingthe crystal supports located Within and spaced from the metal housing.

2. A temperature-controlled piezo-electric crystal mounting thatcomprise a base, an inner housing formed of insulative material mountedon said base and definin a crystal chamber, an outer housing disposed inspaced relationship to the inner housing and defining therewith aheatinsulated space, a heat-conducting housing within said spacedisposed in spaced relationship to the inner housing, an electric heatersupported upon the heat-conducting housing, and a thermostat supportedupon the heat-conducting housin controlling operation of the heater andresponsive to temperature variations Within the outer housing.

3. A temperature-controlled piezo-electric crystal mounting thatcomprises a base, an inner housing formed of insulative material mountedon said base and defining a crystal chamber, an outer housing disposedin spaced relationship i to the inner housing and defining therewith aheat-insulated space, a heat-conducting housing within said spacedisposed in closely spaced relationship to the inner housing, anelectric heater supported upon the heat-conducting housing, and athermostat supported upon the heat-conducting housing controllingoperation of the heater and responsive to temperature variations withinthe outer housing,

4. A mounting according to claim 2 in which the inner and outer housingsare formed of heatinsulating material,

5. A mounting according to claim 2 in which the base is supported upon apedestal formed on a inner portion of the outer housing.

6. A mounting according to claim 2 in which a, central portion of thebase is supported upon a pedestal formed on an inner portion of theouter housing.

7. A mounting according to claim 2 in which only a central portion ofthe base is supported upon a pedestal formed on an inner portion of theouter housing, while a remaining poition of said base forms, inconjunction with the portion adjacent said pedestal, a channel for leadscon necting contact pins with associated crystals.

SAMUEL A. BOKOVOY.

